Auxiliary backrest for a chair

ABSTRACT

The auxiliary backrest for a chair includes a support and an auxiliary backrest body. The support has two rails. Each rail is formed by a surrounding wall and a side wall. An open trough is formed within the two rails. The trough has an inlet. The auxiliary backrest body has a back portion with a pair of elastic sheets. Each elastic sheet has a fixing end connected to the back portion and an elastic end corresponding to the two rails. Each elastic end has an insert portion inserted into the trough. A distance between two outer ends of the two insert portions is slightly greater than a width of the trough. When the insert portions are compressedly inserted into the trough, the elastic ends can be held between the rails by the elasticity thereof.

BACKGROUND OF THE INVENTION 1. Technical Field

The invention relates to chairs, particularly to chair backs.

2. Related Art

To increase sitting comfort of chairs, sufficient and smooth support from a chair back to a user's back is an essential factor. When sitting for a long time, users of chairs will feel backache or users' vertebrae may be deformed if their backs have no proper support.

Adding an auxiliary backrest onto a chair back to enhance support to a user's waist and/or back has been an available solution for a long time. Especially for a chair with a back formed by mesh or fabric as shown in FIG. 1, this kind of chair particularly needs such an auxiliary because it lacks an ample foam to support a user's waist and/or back.

Most of currently existing auxiliary backrests use screws to fasten the backrest onto a frame of a chair back. Although it looks firm, it completely requires manual operation, which means long manufacturing time and being adverse to mass production. Furthermore, this backrest cannot be adjusted in position, so it cannot satisfy various users with different body types.

SUMMARY OF THE INVENTION

An object of the invention is to provide an auxiliary backrest for a chair, which can be easily assembled without tools.

Another object of the invention is to provide an auxiliary backrest for a chair, which can be adjusted in position to satisfy various requirements of different users.

To accomplish the above objects, the auxiliary backrest for a chair of the invention includes a support and an auxiliary backrest body. The support has two rails. Each rail is formed by a surrounding wall and a side wall. An open trough is formed within the two rails. The trough has an inlet. The auxiliary backrest body has a back portion with a pair of elastic sheets. Each elastic sheet has a fixing end connected to the back portion and an elastic end corresponding to the two rails. Each elastic end has an insert portion inserted into the trough. A distance between two outer ends of the two insert portions is slightly greater than a width of the trough. When the insert portions are compressedly inserted into the trough, the elastic ends can be held between the rails by the elasticity thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a conventional meshed chair back;

FIG. 2 is an exploded view of the invention;

FIG. 3 is an assembled view of the invention;

FIG. 4 is a partially enlarged view of the rail of the invention;

FIG. 5 is a schematic view showing the auxiliary backrest body and the support before assembling;

FIG. 6 is a schematic view showing the auxiliary backrest body and the support after assembling; and

FIG. 7 is a schematic view showing the auxiliary backrest body being adjusted on the support.

DETAILED DESCRIPTION OF THE INVENTION

Please refer to FIGS. 2-4. The auxiliary backrest body 1 of the invention is mounted on a support 3 in the chair back 2 for providing sufficient support to a user's back.

The auxiliary backrest body 1 of the invention has a pad portion 10 for supporting a user's waist or back and a back portion 11 for connecting the support 3 of the chair back 2.

To connect and fix the auxiliary backrest body 1, the support 3 is provided with two rails 30 and at least one positioning aperture 31. The positioning aperture 31 is located between the two rails 30 for enhancing fixing strength between the support 3 and the auxiliary backrest body 1. Preferably, in the shown embodiment, there is a plurality of positioning apertures 31, 32 in the support 3. The positioning apertures 31, 32 are longitudinally arranged between the rails 30 for offering the auxiliary backrest body 1 to be able to be positioned at different positions.

Please refer to FIG. 4. Each rail 30 is formed by a surrounding wall 300 connecting the support 3 and a side wall 301. An open trough 302 is formed within the two rails 30. The trough 302 has an inlet 30 a. The inlet 30 a is provided with a guide plate 303 which is inward inclined.

Please refer to FIG. 5. The back portion 11 of the auxiliary backrest body 1 is provided with a pair of elastic sheets 12 and a protrusion 13 between the two elastic sheets 12. Each elastic sheet 12 has a fixing end 120 connected to the back portion 11 and an elastic end 121 corresponding to the trough 302. The elastic end 121 has an insert portion 122 inserted into the trough 302. Preferably, the back portion 11 is formed with two openings 110 for separately allowing the elastic ends 121 to pass through the back portion 11. The insert portions 122 project from the back portion 11. The openings 110 provide the elastic ends 121 a moving space, prevent the elastic sheets 12 from excessively projecting from the back portion 11 to be easily broken and prevent the auxiliary backrest body 1 from excessively projecting from the support 3 to unmake the supporting curve of the chair back.

A distance D1 between two outer ends of the two insert portions 122 is slightly greater than a width of the trough 302. When the insert portions 122 are compressedly inserted into the trough 302, the two insert portions 122 will elastically press the surrounding walls 300, so that the auxiliary backrest body 1 can be held between the rails 30 by the elasticity thereof. The elasticity can be adjusted by setting the difference between the distances D1 and D2. The greater the difference is, the more the deformation of the two elastic ends 121 is and the more the elasticity is. Additionally, the elastic sheets 12 can be made of different materials to form different elasticity.

When assembling, as shown in FIGS. 5 and 6, the insert portions 122 are put into the inlet 30 a of the rails 30 first, the insert portions 122 will be pressed by the guide plates 303 to accumulate elasticity. After the insert portions 122 has passed the guide plates 303 to restore, the insert portions 122 will generate a force onto the surrounding walls 300 and the side walls 301 will prevent the insert portions 122 from escaping. As a result, the auxiliary backrest body 1 can be held between the two rails 30. Meanwhile, the protrusion 13 will fall into one of the positioning apertures 31 to enhance fixing strength of the auxiliary backrest body 1.

The auxiliary backrest body 1 can be slid in the trough 302 to change position. This can satisfy various requirements of different users. The positioning apertures 31, 32 longitudinally arranged between the rails 30 can help the auxiliary backrest body 1 to be positioned. As shown in FIG. 7, when the elastic sheets 12 are being slid in the trough 302, the protrusion 13 can be forced to escape one of the positioning apertures 31 to enter another one. Preferably, the protrusion 13 is of a substantial V-shape to have proper flexibility. The bottom 310 of each of the positioning apertures 31 is of an arced shape to help the protrusion 13 to escape. 

1. A backrest for a chair, comprising: a chair back, being a hollow frame; a support, mounted in a hollow portion of the chair back, having two rails in a substantially vertical direction, each rail being formed by a surrounding wall and a side wall, an open trough being formed in the two rails, and the trough having an inlet; an auxiliary backrest body, having a back portion with a pair of elastic sheets and a pad portion for supporting a user's waist or back, each elastic sheet having a fixing end connected to the back portion and an elastic end corresponding to the two rails, and each elastic end having an insert portion inserted into the trough; wherein a distance between two outer ends of the two insert portions is slightly greater than a width of the trough.
 2. The backrest of claim 1, wherein the inlet is provided with a guide plate which is inwardly inclined.
 3. The backrest of claim 1, wherein the back portion is formed with two openings for separately allowing the elastic ends to pass through the back portion, and the insert portions project from the back portion.
 4. The backrest of claim 1, wherein the support is provided with a positioning aperture between the two rails, the auxiliary backrest body is provided with a protrusion between the two elastic sheets, and the protrusion enters the positioning aperture.
 5. The backrest of claim 1, wherein the support is provided with a plurality of positioning apertures arranged in a line between the two rails, the auxiliary backrest body is provided with a protrusion between the two elastic sheets, and the protrusion enters one of the positioning apertures.
 6. The backrest of claim 4, wherein the protrusion is of a substantial V-shape.
 7. The backrest of claim 6, wherein a bottom of the positioning aperture is of an arced shape.
 8. The backrest of claim 5, wherein the protrusion is of a substantial V-shape.
 9. The backrest of claim 8, wherein a bottom of each of the positioning apertures is of an arced shape. 